JP2012036075A - Method for producing silicate glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing silicate glass which has excellent foam quality without limiting the amount of S in a glass raw material, and particularly, an LiO-AlO-SiO-based crystalline glass which is used in a production of an LiO-AlO-SiO-based crystallized glass.SOLUTION: The production method for the silicate glass includes producing the silicate glass using the glass raw material which has an S inclusion amount of 15 ppm or more in terms of SO, wherein an SiOraw material having an average particle diameter of 45 to 180 μm is used.

Description

The present invention relates to a method for producing silicate glass, and in particular, Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystalline glass used for producing Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass. It relates to a method of manufacturing.

  Conventionally, various glasses have been developed and put into practical use as silicate glasses.

For example _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized glass, main crystal as β- quartz solid solution _{(Li 2 O · Al 2 O} 3 · nSiO 2 [ provided that n ≧ 2]) and β- spodumene solid solution ( Li ₂ O.Al ₂ O ₃ .nSiO ₂ (where n ≧ 4]) is precipitated, and thus has features of extremely low expansion and high mechanical strength. Therefore, it has excellent thermal properties. In addition, since the precipitated crystal can be changed by changing the heat treatment conditions in the crystallization step, the transparent crystallized glass and β-spodumene in which β-quartz solid solution is precipitated from the original glass (crystalline glass) having the same composition. Both white opaque crystallized glass on which a solid solution is deposited can be produced, and can be used properly depending on the application.

Taking advantage of such features, Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass has conventionally been used for high-tech product substrates such as petroleum stove and wood stove front windows, color filters and image sensor substrates, Top plate substrates for electromagnetic cookers and gas cookers, window glass for fire doors, reflector base materials used in projectors such as liquid crystal projectors and light source lamps for lighting, setters for heat treatment of electronic components and plasma display panels It is used for a wide variety of applications such as shelf boards for microwave ovens, electronic parts and precision machine parts.

JP 11-228180 A JP 2004-67408 A

By the way, when manufacturing glass with high temperature viscosity, it is necessary to melt at high temperature. For example, when manufacturing crystallized glass as described above, the melting temperature of the original glass (crystalline glass) is a high temperature exceeding 1600 ° C. Glass with high viscosity is difficult to remove bubbles, so it is difficult to remove bubbles in the glass melt. Therefore, As ₂ O ₃ and Sb ₂ O ₃ are widely used as fining agents. However, As ₂ O ₃ and Sb ₂ O ₃ are highly toxic and may pollute the environment during the glass production process or waste glass treatment. As a solution to this problem, the use of SnO ₂ , CeO ₂ , Cl or the like instead of As ₂ O ₃ or Sb ₂ O ₃ has been studied. For example, Patent Document 1 discloses a Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass in which SnO ₂ and Cl are used in combination as clarifying agents.

However, even if SnO ₂ , CeO ₂ , Cl, or the like is used as a clarifying agent instead of As ₂ O ₃ or Sb ₂ O ₃ , the Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallinity is always excellent in foam quality. There is a problem that glass cannot be obtained. This tendency is particularly noticeable when producing in a continuous production tank kiln. When melted in a laboratory using a crucible in a stationary condition, a product with good foam quality can be obtained, whereas when applied to a continuous production tank kiln, a product with good foam quality is often not obtained.

  The cause is the reboil of the S (sulfur) component mixed from the glass raw material. Therefore, it is conceivable to reduce the S component mixed from the glass raw material as much as possible. However, from the viewpoint of reducing raw material costs and ease of recycling waste glass, it is difficult to reduce the amount of S contained in the glass raw material.

  The objective of this invention is providing the manufacturing method of the silicate glass excellent in the foam quality using the tank kiln of continuous production, without restrict | limiting the amount of S in a glass raw material.

Patent Document 2 discloses the particle size of the SiO ₂ raw material used for the production of alkali-free glass, but this document does not take into account the S component reboil.

That is, the method for manufacturing silicate glass of the present invention is a method for producing a silicate glass to produce a silicate glass using a glass raw material containing more than 15ppm of S content converted to SO _3, average particle size 45 It is characterized by using a SiO ₂ raw material of ˜180 μm. Here, the “S content contained in the glass raw material” was determined by immersing the analysis sample by alkali melting with Na ₂ CO ₃ , filtering with a filter paper, and then stirring the solution with an ion exchange resin and filtering again. Thereafter, the values measured by ion chromatography are converted to SO ₃ . In addition, the “average particle size” of the SiO ₂ raw material is a graph showing the ratio of passing through the sieve using a sieve having openings of various sizes. It means the size of the opening through which 50% amount passes.

According to the said structure, even if it does not intentionally reduce the amount of S in a glass raw material, the silicate glass excellent in foam quality can be obtained. That is, the SiO ₂ raw material is easily dissolved in the initial raw material melting stage, and the S component is less likely to be dissolved in the glass melt, so that reboil caused by the S component is less likely to occur.

In the present invention, it is preferable to use a SiO ₂ raw material having an average particle diameter of 50 to 150 μm.

In the present invention, silicate glasses _is preferably a _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized glass. Here, the “crystalline glass” means an amorphous glass having a property of being crystallized by precipitating crystals from the glass matrix upon heat treatment. “Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass” means containing Li ₂ O, Al ₂ O ₃ and SiO ₂ as essential components, and β-quartz solid solution and / or β-spodumene when heat-treated. It means crystalline glass having the property of precipitating a solid solution as a main crystal.

If the said structure is employ | adopted, the effect of this invention can be enjoyed exactly. That is, the S component mixed from the raw material or the like is contained as an impurity in the glass melt. In particular, lithium carbonate (Li ₂ CO ₃ ) used as a Li ₂ O raw material may contain a large amount of S component as an impurity. In addition, since Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass has a low S solubility in the glass melt, the S component exists in an unstable state in the melt. The S component is easily gasified by a slight change in the state (for example, redox, composition change, temperature change). Therefore, the merit of adopting the method of the present invention is great.

In the present invention, silicate glass, by mass _{percentage, SiO 2 50~80%, Al 2} O 3 12~30%, Li 2 O 1~6%, 0~5% MgO, 0~10% ZnO, Li ₂ O— containing BaO 0-8%, Na ₂ O 0-5%, K ₂ O 0-10%, TiO ₂ 0-8%, ZrO ₂ 0-7%, P ₂ O ₅ 0-7% Al ₂ O ₃ —SiO ₂ based crystalline glass is preferred. In the present specification, “%” means “% by mass” unless otherwise specified.

In the present invention, it is preferable that the content of _As 2 _{O 3} and _Sb 2 _{O 3} is prepared a glass raw material so that 0.1 wt% or less in total. In addition, “the content of As ₂ O ₃ and Sb ₂ O ₃ is 0.1% by mass or less” means that not only an intentionally added As raw material or Sb raw material but also an As component or Sb mixed as an impurity. It means that the total amount including components is 0.1% by mass or less.

Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass has an S component in an unstable state in the melt because the S solubility of the glass melt is low. The S component is easily gasified by a slight change in the state (for example, redox, composition change, temperature change). However, even under such conditions, when As ₂ O ₃ or Sb ₂ O ₃ is used as a fining agent, a large amount of fining gas released from these fining agent components causes S in the glass melt. The component is easily removed. Further, when As ₂ O ₃ or Sb ₂ O ₃ is present in the melt, these fining components oxidize the S component, and the S component is stably present in the glass melt in the state of SO ₄ ^2−. There is a tendency to make it. Therefore, SO ₄ ²⁻ is hardly decomposed into SO ₂ (gas) + O ₂ , and it becomes easy to suppress gasification.

However, clarifiers other than As ₂ O ₃ and Sb ₂ O ₃ have a small effect of removing the S component from the glass melt and an effect of stably presenting the S component in the glass melt in the state of SO ₄ ^2−. . As a result, a so-called reboil phenomenon in which the S component foams as SO ₂ gas or the like from the glass melt easily occurs. This phenomenon is due to the large fluctuations in the raw material input conditions and melting conditions in the continuous production tank kiln, as compared to the case of melting in a stationary state as in a crucible test in a laboratory, and refractories are also eluted. The glass state is likely to change, and reboiling due to the S component is likely to occur. This is a phenomenon that has been clarified by performing continuous production of silicate glass without containing As ₂ O ₃ or Sb ₂ O ₃ . For example, if 1 ppm of S component in terms of SO ₃ is gasified, it is calculated that bubbles of several thousand to several tens of thousands / kg are generated. Therefore, how to prevent reboiling of S component is Li ₂ O—Al with less bubbles. _This is very important in obtaining ₂ O ₃ —SiO ₂ -based crystalline glass. Therefore, the merit of adopting the method of the present invention is great.

  In this invention, it is preferable to add 0.04-0.3 mass% of chloride in conversion of Cl with respect to 100 mass% of glass raw materials.

  If the said structure is employ | adopted, it will become possible to clarify glass sufficiently.

In the present invention, it is preferable that the average particle size of the SiO ₂ raw material is 60 to 120.

  In the present invention, it is preferable to melt the glass in a tank kiln.

  If the said structure is employ | adopted, the effect of this invention can be enjoyed more exactly. In other words, compared to melting in a stationary state such as in a crucible test in a laboratory, in a continuous production tank kiln, there are large fluctuations in raw material charging conditions and melting conditions, and there is also leaching of refractories, so glass State change is likely to occur, reboiling due to the S component is likely to occur, and it is difficult to obtain a product with good foam quality. Therefore, the merit of adopting the method of the present invention is great.

The method for producing a silicate glass of the present invention is a method for producing a silicate glass. The silicate glass is not particularly limited as long as it is a glass containing SiO ₂ such as Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass, non-alkali glass, etc. In particular, the S component is easily mixed from the raw material. , yet it is preferably applied to the production of _{Li 2 O-Al 2 O 3} -SiO 2 based crystallized glass is low solubility of S component.

In the following description, the present invention will be described using a method for producing Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass.

First, a glass raw material batch is prepared so as to have a desired composition. The raw material batch in the resulting glass mass%, for example _{SiO 2 50~80%, Al 2 O} 3 12~30%, Li 2 O 1~6%, 0~5% MgO, 0~10% ZnO, _{BaO 0~8%, Na 2 O 0~5} %, K 2 O 0~10%, TiO 2 0~8%, ZrO 2 0~7%, so as to have a composition of _P 2 O 5 _0~7% Can be prepared.

At this time, as SiO ₂ raw material, it is important to use a SiO ₂ material of average particle size 45～180Myuemu. The reason will be described below.

In the case of a low S solubility glass such as Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass, the amount of S in the glass melt is affected by the initial melting conditions in which the raw material is dissolved. When the melting process of the raw material in the Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass is analyzed in detail, an initial melt having a small SiO ₂ component is first formed, and the SiO ₂ raw material is dissolved therein. Looking at the glass melt from the viewpoint of acidity, since SiO ₂ is a component with high acidity, the initial melt with little SiO ₂ component has low acidity, and the acidity increases as the SiO ₂ raw material dissolves. Rises. Since the S component is more easily dissolved in the melt as the acidity of the glass is lower, it is considered that the lower the acidity of the initial melt, the easier it is to become a glass melt containing more S component. In other words, if SiO ₂ is easily dissolved in the initial raw material melting stage, it becomes difficult for the S component to dissolve in the glass melt, and as a result, reboil caused by the S component is less likely to occur. It is desirable to facilitate the dissolution of the SiO ₂ raw material this reason by reducing the particle size of the SiO ₂ raw material.

Specifically, the SiO ₂ raw material has an average particle size of 180 μm or less, preferably 160 μm or less, more preferably 150 μm or less, still more preferably 120 μm or less, and particularly preferably 100 μm or less. However, if the particle size of the SiO ₂ raw material is too small, when the raw material is added, only the surface is quickly melted by radiant heat, and the internal S component is difficult to volatilize and dissipate. As a result, the amount of S in the glass melt is not reduced. Therefore, it is preferable to prevent the dissolution speed of the SiO ₂ raw material from becoming too high. Specifically, the average particle diameter of the SiO ₂ raw material is preferably 45 μm or more, 50 μm or more, and particularly preferably 60 μm or more.

In the present invention, there is no need to particularly limit the amount of S mixed as an impurity in the glass raw material batch. Specifically, the S component may be 15 ppm or more, 20 ppm or more, 50 ppm or more, and further 100 ppm or more in terms of SO ₃ . The larger the amount of S in the glass raw material, the more advantageous it is in reducing the raw material cost and facilitating the recycling of waste glass and the like. However, if the amount of S in the glass raw material is too large, it becomes difficult to reduce the amount of S contained in the glass, and it becomes difficult to suppress reboil of the S component in the method of the present invention. Therefore, it is preferable to limit the amount of S in the glass raw material to 500 ppm or less, preferably 300 ppm or less, more preferably 150 ppm or less in terms of SO ₃ .

  Moreover, it is not necessary to restrict | limit especially about the cullet mixed with a raw material in order to reuse glass. However, since the cullet is easily dissolved, if the cullet is too fine, it quickly melts by radiant heat and the internal S component is difficult to volatilize and escape, so the average particle size of the cullet is preferably 1000 μm or more.

  The reason for limiting the glass composition as described above is shown below.

SiO ₂ is a component that forms a glass skeleton and constitutes a crystal, and its content is 50 to 80%, preferably 52 to 77%, and more preferably 54 to 75%. If the content of SiO ₂ is too small, the thermal expansion coefficient becomes too large, and if the content of SiO ₂ is too large, glass melting becomes difficult.

Al ₂ O ₃ is a component that forms a glass skeleton and constitutes a crystal, and its content is 12 to 30%, preferably 13 to 28%, and more preferably 14 to 26%. When the content of Al ₂ O ₃ is small, the chemical durability is lowered and the glass is easily devitrified. On the other hand, if the content of Al ₂ O ₃ is too large, the viscosity of the glass becomes too high and glass melting becomes difficult.

Li ₂ O is a crystal component, has a large effect on crystallinity, and functions to lower the viscosity of the glass. Li also combines with chlorine in the melt to become relatively stable LiCl, which volatilizes and acts as a clarification gas. Therefore, in the Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass, sufficient clarification power is obtained by containing a large amount of Li ₂ O even if Cl is used alone as a clarifier. It becomes possible. The content of Li ₂ O is 1 to 6%, preferably 1.2 to 5.5%, more preferably 1.4 to 5.0%. In particular, when an clarifier such as SnO ₂ or CeO ₂ is not used and the clarifier is Cl alone, Li ₂ O is preferably 3% or more. When the Li 2 _O content is too small weakens the crystallinity of the glass, the thermal expansion coefficient becomes too large. Moreover, when it becomes transparent crystallized glass, a crystal | crystallization thing becomes easy to become cloudy, and when it is set as white crystallized glass, a whiteness fall will occur easily. In addition, clarification with Cl alone becomes difficult. On the other hand, if the content of Li ₂ O is too large, the crystallinity becomes too strong, the glass is devitrified, the metastable β-quartz solid solution cannot be obtained, and the crystal becomes cloudy, and the transparent crystal It becomes impossible to obtain a vitrified glass.

  The content of MgO is 0 to 5%, preferably 0 to 4.5%, more preferably 0 to 4%. If the content of MgO is too large, the crystallinity becomes strong, the amount of precipitated crystals increases, and the impurity coloring becomes too strong.

  The content of ZnO is 0 to 10%, preferably 0 to 8%, more preferably 0 to 6%, and still more preferably 0 to 5%. When there is too much content of ZnO, crystallinity will become strong, the amount of precipitated crystals will increase, and impurity coloring will become strong too much.

  The total content (total amount) of MgO and ZnO is 0 to 10%, particularly 0 to 8%, more preferably 0 to 6%. If the total amount of these components is too large, the crystallized product tends to be strongly colored.

  The content of BaO is 0 to 8%, preferably 0.3 to 7%, more preferably 0.5 to 6%. If the content of BaO is too large, a sufficient amount of crystals cannot be obtained to inhibit crystal precipitation, and the thermal expansion coefficient becomes too large. Furthermore, when obtaining transparent crystallized glass, the crystallized product tends to become cloudy.

The content of Na ₂ O is 0 to 5%, preferably 0 to 4%, more preferably 0 to 0.35%. Na 2 _O is not sufficient amount of crystals is obtained and the content is too much weakened crystallinity, and the thermal expansion coefficient becomes too large. Furthermore, when obtaining transparent crystallized glass, the crystallized product tends to become cloudy.

The content of K ₂ O is 0 to 10%, preferably 0 to 8%, more preferably 0 to 6%, and further preferably 0 to 5%. K 2 _O without sufficient amount of crystals is obtained and the content is too much weakened crystallinity, and the thermal expansion coefficient becomes too large. Furthermore, when obtaining transparent crystallized glass, the crystallized product tends to become cloudy.

The content of Na ₂ O and _{K 2} O 0 to 12% in the total amount (total amount), particularly 0-10%, and further preferably 0-8%. If the total amount of these components is too large, the thermal expansion coefficient tends to increase. Moreover, when obtaining transparent crystallized glass, a crystal substance becomes easy to become cloudy.

TiO ₂ is a nucleating agent, and its content is 0 to 8%, preferably 0.3 to 7%, more preferably 0.5 to 6%. When the content of TiO ₂ is too large, impurity coloring becomes remarkable.

ZrO ₂ is a nucleating agent, and its content is 0 to 7%, preferably 0.5 to 6%, more preferably 1 to 5%. When the content of ZrO ₂ is too large with glass melting becomes difficult, devitrification of the glass increases.

P ₂ O ₅ is a component for improving the crystallinity of the glass, and its content is 0 to 7%, preferably 0 to 6%, more preferably 0 to 5%. When the content of P ₂ O ₅ is too large too thermal expansion coefficient is increased, also it tends to white turbidity crystals in the case of obtaining transparent crystallized glass.

In the present invention, various components other than the above can be added as the glass composition. For example, CaO may be contained up to 5% and B ₂ O ₃ may be contained up to 10%. As a colorant, for example, V ₂ O ₅ can be contained up to 1.5%, preferably 1.0%, more preferably 0.8%.

Furthermore, chloride is added to the glass raw material batch as a clarifier as necessary. When chloride is added, the amount added is 0.04 to 0.3%, preferably 0.08 to 0.2%, and more preferably 0.8% in terms of Cl with respect to 100% by mass of the glass raw material batch. 1 to 0.18%. Moreover, you may add Ce compound and Sn compound. When adding Ce compound, the addition amount of the content in the glass raw material batch in terms of CeO _2, 0 to 0.2%, preferably from 0 to 0.15%, more preferably from 0 to 0.1% To be. When adding Sn compound, the addition amount of the content in the glass raw material batch in terms of SnO _2, from 0 to 0.6%, preferably from 0 to 0.3%, more preferably 0 to 0.2% To be. Note that As ₂ O ₃ and Sb ₂ O ₃ are highly toxic and may contaminate the environment during the glass production process or waste glass treatment. Therefore, the total amount including impurities as an impurity is 0.1. It is preferable to set it as mass% or less. In particular, As ₂ O ₃ and Sb ₂ O ₃ are desirably not intentionally added as raw materials. In applications where the coloring of glass is strictly regulated, addition of Ce compounds should be avoided. Also, it is better to limit the amount of Sn compound added, for example, 0.5% or less.

  Next, the glass raw materials are homogeneously mixed and then melted in a melting facility, particularly a tank kiln capable of continuous production. In the case of the glass having the above composition, the melting condition is preferably about 20 to 200 hours at a maximum temperature of 1600 to 1800 ° C.

Subsequently, the glass melt is formed into a desired shape to obtain Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystalline glass. As a molding method, various methods such as roll molding, press molding, and float molding can be employed.

Thus, it is possible to obtain a silicate glass excellent in foam quality (Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystalline glass in the above example) without reducing the S content in the raw material. it can.

The obtained Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass is then subjected to a heat treatment for crystallization, followed by post-processing such as cutting, polishing, bending, stretch molding, It can be used for various purposes. The heat treatment is carried out at 700 to 800 ° C. for 1 to 4 hours for nucleation. When a transparent crystallized glass is formed, heat treatment is performed at 800 to 950 ° C. for 0.5 to 3 hours to precipitate β-quartz solid solution. Let In addition, when a white opaque crystallized glass is formed, a β-spodumene solid solution may be precipitated by heat treatment at 1050 to 1250 ° C. for 0.5 to 2 hours after nucleation.

  As means for further reducing the amount of S in the silicate glass and further making reboil less likely to occur, (1) a method of increasing the amount of water in the glass melt in the presence of Cl, (2) optimizing the batch melting temperature A method, (3) a method of optimizing the melting efficiency, and the like can be employed. By appropriately combining these methods, it becomes possible to obtain a silicate glass having a lower S content and being difficult to reboil. Each method will be described in detail below.

(1) Method for adjusting water content in glass melt According to the inventors' investigation, Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass having low S solubility is soda lime glass having high S solubility. Unlike the above, even if the water content is simply increased, the S content in the glass melt cannot be reduced. However, if Cl is present in the glass melt, the S content can be significantly reduced. Although the details of this mechanism are unknown, it is considered that HCl gas is generated when water and Cl coexist, and the S component volatilizes and the S content in the glass melt decreases as the gas is generated. As the amount of water in the glass melt increases, the effect of reducing the amount of S increases. In order to increase the water content in the glass melt, a method using a raw material with a high water content, increasing the water content in the combustion gas during glass melting, or using water vapor bubbling in the molten glass is adopted. be able to. The water content of the glass melt can be represented by the β-OH value of the glass. Specifically, in the case of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass, β-OH after crystallization is 0.2 / mm or more, particularly 0.3 / mm or more, and further preferably 0.8. It is preferable that it is 35 / mm or more. The β-OH value is a value calculated by the following formula.

β-OH value (/ mm) = {log (T3850 / T3500)} / t
T3850: transmittance of 3850cm ^-1 T3500: 3500cm minimum transmittance of absorption band near ^-1 t: thickness of sample (mm)

(2) Method of optimizing batch melting temperature Batch melting temperature is a temperature at which log η = 2.3 to 3.0, particularly a temperature at which log η = 2.3 to 2.9, and further log η = 2.4. It is desirable to set the temperature to ˜2.9. Here, η is dPa · s. When the batch melting temperature is high, the batch is easily melted, and when the raw material is charged, only the surface is quickly melted by radiant heat, and the internal S component is difficult to volatilize and dissipate. On the other hand, when the batch melting temperature is low, the SiO ₂ raw material becomes difficult to dissolve, so an initial melt with low acidity is formed, and the S content tends to increase. The batch melting temperature can be measured using a radiation thermometer on the side wall near the glass raw material batch charged into the glass melting furnace.

(3) Method of optimizing melting efficiency If the melting time is lengthened, uncleared bubbles in the glass melt can be removed. In addition, the amount of S can be reduced. However, long-time melting reduces productivity and makes it difficult to provide inexpensive glass. If the melting time is too long, a heterogeneous layer tends to be formed on the glass surface due to volatilization. As described above, in the glass having low S solubility, the S component is easily gasified by a slight change such as a composition change. Under such circumstances, it is desirable to appropriately manage the melting time. As an index of melting time, melting efficiency (melting area / flow rate) can be employed. Specifically, the melting efficiency is preferably 1.0 to 5.0 m ² / (t / day), particularly 1.5 to 4.5 m ² / (t / day).

  Hereinafter, the present invention will be described based on examples and comparative examples.

  Table 1 shows examples (sample Nos. 2 and 3) and comparative examples (samples No. 1 and 4) of the present invention.

  Each sample was prepared as follows.

First, by mass percentage, SiO ₂ 67%, Al ₂ O ₃ 23%, Li ₂ O 4%, BaO 1.5%, Na ₂ O 0.5%, TiO ₂ 2%, ZrO ₂ 2% Silica sand, alumina, lithium carbonate, barium nitrate, sodium nitrate, titanium oxide, zirconium oxide and the like were mixed, and NaCl was mixed uniformly so as to contain 0.2 mass% of Cl. At this time, a raw material having an average particle diameter shown in the table was used as the SiO ₂ raw material.

Next, this raw material batch was put into a refractory kiln (tank kiln for continuous production) by oxygen combustion and melted at a melting efficiency of 2.5 m ² / (t / day). Next, the glass melt was stirred with a platinum stirrer, roll-formed to a thickness of 4 mm, and further cooled to room temperature in a slow cooling furnace.

  Thereafter, the crystalline glass sample obtained by cutting to a predetermined length was measured for the presence or absence of reboyl. The results are shown in Table 1.

As is apparent from the table, No. 1 using an SiO ₂ raw material having an average particle diameter in the range of 45 to 180 μm. No reboiling occurred in 2 and 3.

The amount of SO ₃ in the raw material and the glass is determined by immersing the analysis sample with Na ₂ CO ₃ by alkali melting, filtering with a filter paper, then stirring the liquid with an ion exchange resin, filtering again, It is the value obtained by measuring by chromatography.

  The presence or absence of reboil is calculated by converting the number of bubbles in the glass collected before stirring with the platinum stirrer and the glass after molding into the number of bubbles per kg, and the number of bubbles in the glass after molding occurs in the glass before stirring. It was judged that reboiling had occurred when the number of bubbles was more than twice.

  Subsequently, the crystalline glass sample was put in an electric furnace, heat-treated according to the following two schedules for crystallization, and then cooled in the furnace.

(1) Nucleation: 780 ° C.-2 hours → Crystal growth: 900 ° C.-3 hours (2) Nucleation: 780 ° C.-2 hours → Crystal growth: 1160 ° C.-1 hour The temperature was 300 ° C./h, and the temperature from the nucleation temperature to the crystal growth temperature was 100 to 200 ° C./h.

  About each obtained sample, the main crystal | crystallization and the external appearance were evaluated. As a result, when any sample was heat-treated according to the schedule (1), a transparent crystallized glass in which a β-quartz solid solution was precipitated as a main crystal was obtained. When heat treatment was performed according to schedule (2), a white opaque crystallized glass in which a β-spodumene solid solution was precipitated as a main crystal was obtained.

  The main crystal was evaluated using an X-ray diffractometer.

  The appearance was visually observed.

The Li ₂ O—Al ₂ O ₃ —SiO ₂ crystalline glass produced by the method of the present invention can be used for various applications by crystallization. Specifically, front windows such as oil stoves and wood stoves, substrates for high-tech products such as color filters and image sensor substrates, substrates for top plates such as electromagnetic cookers and gas cookers, window glass for fire doors, and liquid crystal projectors Examples thereof include a reflector substrate used for a projector such as a projector and a light source lamp for illumination, a heat treatment setter for an electronic component or a plasma display panel, a shelf for a microwave oven, an electronic component, or a precision mechanical component.

Further, the method of the present invention is not limited to Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystalline glass, but can be applied as a method for producing non-alkali glass used as a liquid crystal display substrate, for example. .

Claims (8)

The S content a method for producing a silicate glass to produce a silicate glass using a glass raw material containing 15ppm or more converted to SO _3, and characterized by the use of SiO ₂ raw material having an average particle diameter of 45~180μm A method for producing silicate glass. Method for producing a silicate glass according to claim 1, characterized in that the use of SiO ₂ raw material having an average particle size of 50 to 150 [mu] m. The method for producing a silicate glass according to claim 1, wherein the silicate glass is Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystalline glass. Silicate glass, by mass _{percentage, SiO 2 50~80%, Al 2} O 3 12~30%, Li 2 O 1~6%, 0~5% MgO, 0~10% ZnO, BaO 0~8% _{, Na 2 O 0~5%, K} 2 O 0~10%, TiO 2 0~8%, ZrO 2 0~7%, P 2 O 5 containing _{0~7% Li 2 O-Al 2} O 3 - method for producing a silicate glass according to any one of claims 1 to 3, characterized in that the SiO ₂ based crystallized glass. The silicate glass according to any one of claims 1 to 4, wherein the glass raw material is prepared so that the total content of As ₂ O ₃ and Sb ₂ O ₃ is 0.1 mass% or less. Manufacturing method.   The method for producing a silicate glass according to any one of claims 1 to 5, wherein 0.04 to 0.3 mass% of chloride in terms of Cl is added to 100 mass% of the glass raw material. Method for producing a silicate glass according to any one of claims 1 to 6, wherein the average particle size of the SiO ₂ raw material is 60 to 120. The method for producing a silicate glass according to any one of claims 1 to 7, wherein the glass is melted in a tank kiln.